The present invention is directed to mounting arrangements in which coulters are supported by and connected to portable tool bars. Numerous arrangements of this general type are shown in the prior art U.S. Pat. Nos. 1,162,934, 1,198,942, 1,790,956, 3,061,018, 3,292,562, 3,319,589, 3,351,139 and 3,799,079. None of these devices provides a locking mechanism which may be selectively positioned relative to the shank so as to permit the coulter to pivot about the shank or to be locked to the shank at the option of the operator.